Holographic reconstruction system with a tracking device for the reconstruction

Abstract

A holographic reconstruction system having spatial light modulators, an eye finder and a position control orients a propagating spatially modulated light wave field toward at least one eye position of an observer's eye, thereby reconstructing a scene in a three-dimensional manner and tracking the same during a position change of the eye position. Unobstructed lateral and axial movement of the observer head to arbitrary eye positions in a tracking region is enabled. The use of additional, planar optical components, which bring about optical aberrations during a position change of observer eyes, are prevented.

1. A holographic reconstruction system for holographically reconstructing object elements of a scene, which system modulates at least one light wave field capable of generating interference with a sequence of video holograms, with the help of a discretely encodable cell structure of modulator cells of spatial light modulator means, said system comprising:
 hologram processor means for: 
 assigning each object element of the scene with a discrete hologram region on the cell structure, whose extent and position depend on position information of the object element in the scene; and 
 computing a code for each hologram region such that each hologram region on the cell structure modulates a partial light wave of the light wave field, and that each modulated partial light wave separately reconstructs the object element assigned to it and then propagates in the form of a light wave cone towards a visibility region; and 
 position controller means for: 
 directing the modulated partial light waves at at least one current eye position of an observer; and 
 tracking it to a changing eye position when the observer moves, so that the fully reconstructed scene is visible in the visibility region for the current eye position; 
 wherein the hologram processor means uses position information of the current eye position 
 to adapt the extent and position of the hologram regions to the current eye position, and 
 to compute the code such that each modulated partial light wave is directed to the current eye position, without light of parasitic diffraction orders entering a used diffraction order. 
 
     
     
       2. The holographic reconstruction system according to  claim 1 , where the hologram processor means consider the eye position information of the current eye positions in order to encode the cell structure dynamically such that the reconstruction system tracks the modulated partial light waves to the current eye position in a tracking range. 
     
     
       3. The holographic reconstruction system according to  claim 1 , where the hologram processor means encode the cell structure dynamically such that the light wave cones form a visibility region at the current eye position by way of coincidence and, if the eye positions change, track the reconstructed object elements by way of re-computing the code. 
     
     
       4. The holographic reconstruction system according to  claim 3 , where the visibility region has a predefined extent, and that the hologram processor means dynamically encode the cell structure such that the extent of the visibility region remains constant irrespective of the distance in front of the spatial light modulator means at which an observer is situated. 
     
     
       5. The holographic reconstruction system according to  claim 1 , where the hologram processor means compute a lens term for the hologram regions depending on the position of the corresponding reconstructed object element and depending on the eye position, and superimpose this lens term with a prism term for directing the reconstructed object element at the eye position. 
     
     
       6. The holographic reconstruction system according to  claim 1 , where the spatial light modulator means comprise at least one spatial light modulator which performs a spatial phase modulation of the wave field which is capable of generating interference. 
     
     
       7. The holographic reconstruction system according to  claim 1 , where the hologram processor means use information about a firmly defined structure of object light points of the scene and compute for each object light point a hologram region whose extent and position depends on both the axial distance of the object light point and the distance of the eye position to the spatial light modulator for each hologram region. 
     
     
       8. The holographic reconstruction system according to  claim 7 , where the modulator cell structure always carries a constant number of discrete hologram regions, irrespective of the content of the current video hologram. 
     
     
       9. The holographic reconstruction system according to  claim 7 , where number of discrete hologram regions depends on a pixel grid, which corresponds with the desired resolution of the holographic reconstruction in the visibility region. 
     
     
       10. The holographic reconstruction system according to  claim 1 , where the scene which is reconstructed with the help of the hologram regions remains at a fix position in space in relation to the current observer window. 
     
     
       11. The holographic reconstruction system according to  claim 1 , where the hologram processor means generate a new functional visibility region when the eye moves axially, in that the hologram processor means redefine the size and position of the hologram regions on the modulator cell structure and adapt the value of the encoded prism term to the current eye position. 
     
     
       12. The holographic reconstruction system according to  claim 1 , where the hologram processor means modify the code of the modulator cell structure when the position of the observer eye changes, in order to adapt the view of the reconstructed scene to the current eye position. 
     
     
       13. The holographic reconstruction system according to  claim 1 , where when the observer moves sideways from one eye position to another, the hologram processor means generally compute and encode such information about the position of the hologram regions on the modulator cell structure, that the position at which the scene is reconstructed changes in relation to the light modulator such that the scene exhibits an equal viewing space in the visibility region of each eye position. 
     
     
       14. The holographic reconstruction system according to  claim 1 , where the hologram processor means check the visibility of the object light points with the help of the ray tracing method if the eye position changes, and adapts the structure of the reconstructed object light points depending on the current eye position. 
     
     
       15. The holographic reconstruction system according to  claim 1 , where a light wave field which propagates in a converging manner illuminates the spatial light modulator means. 
     
     
       16. The holographic reconstruction system according to  claim 1  with a focussing display screen for projecting the light source onto the observer eye.